The present disclosure relates to optical thin-film fabrication and, more particularly, to systems and methods of controlling a deposition rate during optical thin-film fabrication.
In the field of thin-film device fabrication for optical purposes, the design of a multilayered thin-film device targets a specific spectral performance. As each of the layers is formed in a stack, fabrication variability results in a multilayered film that may have inconsistent values of the optical properties of different layers made of the same material. Inconsistencies may arise, for example, from manufacturing variability associated with temperature and pressure control inside a deposition chamber. Once fabrication of the thin-film device is finished and tested, fabrication errors in the thin-film device that are beyond a specified tolerance result in the thin-film device being discarded and fabrication of a new thin-film device is then required. As can be appreciated, this procedure results in waste of time and materials, in detriment of fabrication cost efficiency.
Current fabrication techniques provide real-time monitoring of layer thickness using changes in the mechanical properties of a quartz crystal as a layer is deposited on its surface. However, these techniques fail to provide optical properties relevant to the functionality of the optical thin-film. Furthermore, measurement of mechanical properties of a quartz crystal can be noisy, and thereby result in reduced accuracy.